UserVoice - UserVoice integrates easy-to-use feedback, helpdesk, and knowledge base management tools in one platform that empowers users to speak and companies to understand.

Zendesk - Zendesk is a beautiful, lightweight help-desk solution.

Freshdesk - Freshdesk is a cloud-based customer support software that lets you support customers through traditional channels like phone and email, social channels like Facebook and Twitter, and your own branded community

Zendo - Zendo allows you to sell productized, subscription and custom services. Collaborate and collect payments. Create quotes and invoices. Eliminate multiple tools and enjoy the simplicity.

Canny - Canny helps you collect and organize feature requests to better understand customer needs and prioritize your roadmap.

SendBoard - Send & Receive emails in Trello, where you can collaborate and get more done. For email help desks, CRM, workflow and automation. Add the Power-Up in Trello.